Excellent advice guys. Thanks for the plug Doc. I work for the Steiner distributor for the UK so am most familiar with this range of Bino's.
The Steiners offer very high quality optics combined with a rubber armoured Makralon shell. This makes em pretty indestructible (with a 30 year warranty they have to be) hence the military like them. Steiners principle market was marine, so they build 100% waterproof binoculars designed to put up alot of weather, salt water and hard knocks. They have to be tough. They have carried this build quality across to their wildlife and hunting ranges, so have set new standards in these markets. Combined with cutting edge optical enhancements they only compare at the top end with Swarovski. Just much tougher.
Personally I prefer Porro prism binoculars, they give better 3D rendition, as the object lenses (the ones at the front) are further apart. This makes it much easier to pick objects out from a background. They also have less internal moving parts, so less to go wrong and give better colour rendition as the light doesn't bounce around and interfear so much. The down side - they are bigger and heavier.
Roof prism is the other option, internally they are much more complicated with precision moving parts so are more prone to knocks. but respect them and they will last. The major advantage is that they can be much more compact. Right down to pocket sized. So if weight is the issue this is the way to go.
You get 2 numbers say 10x50 that means 10x magnification (thats quite a bit) and a 50mm object lens. Firstly the magnification. 10x is about as much as you can reasonably hold steady with your hands, and even at this they shake a bit, so really 8x (Steiner say 7x especially for marine use) is more comfortable to use but you just can't see as far!
The 50mm - The diameter of the object lens. This determines how much light they let in, the brighter the image the easier to see. - especially in dark woods. The bigger this number the bigger the bino's (and heavier)
Now the tricky bit, divide one by the other 50/10 to give the "exit pupil", in this case 5 thats mm of the column of light that comes out the back (ocular lens) and into your eye. The pupil of your eye opens to a maximum of 7mm on average, so this is the most light your eye can absorb. So if you buy tiny pocket sized bino's say 10x26 this means you only get a column of light 2.6mm (26/10) in diameter to see with. Obviously your not going to see anywhere near as well with so little light.
Add to that low light in woodland and you really not going to see much at all. We do a fantastic pair of 8x56 "nighthunters" giving that magic 7mm exit pupil designed for dawn and dusk hunting they really are quite incredible.(sorry gratuitous plug)
Nitrogen - it stops em fogging up. Theres 2 sorts "Nitrogen purged" that means they ran nitrogen through them when they built them to evacuate any moisture. Then there is "Nitrogen filled" so its still in them, so no chance of fogging, or water getting in as they are essentially gas tight.
Beyond this it depends on your use and your budget.
The other companies that you might also consider as they do make reasonable binoculars are Swarvoski, Zeiss, Leica and the Best of the rest Bushnell, Bauch and lomb, Canon (who make the best "image stabilised" electronic binoculars if you want more than 10x magnification IMO), Nikon, Pentax, Opticron and Fujinon (again image stabilised specialists)
Other things to watch out for are "eye relief". Important if you wear glasses, as this is the distance from your eyeball that the binoculars will work, without all that black around the edge...
The other thing is close focus, surprisingly useful and often (wait for it) overlooked (boom boom)
Sorry it took so long to reply, i've been trying to post this for days.
Hope its useful
Rich
